Method and system for electron density measurement

ABSTRACT

The present invention provides a diagnostic system for plasma processing, wherein the diagnostic system comprises a multi-modal resonator, a power source, a detector, and a controller. The controller is coupled to the power source and the detector and it is configured to provide a man-machine interface for performing several monitoring and controlling functions associated with the diagnostic system including: a Gunn diode voltage monitor, a Gunn diode current monitor, a varactor diode voltage monitor, a detector voltage monitor, a varactor voltage control, a varactor voltage sweep control, a resonance lock-on control, a graphical user control, and an electron density monitor. The diagnostic system can further provide a remote controller coupled to the controller and configured to provide a remote man-machine interface. The remote man-machine interface. The remote man-machine interface can provide a graphical user interface in order to permit remote control of the diagnostic system by an operator. In addition, the present invention provides several methods of controlling the diagnostic system in order to perform both monitor and control functions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending International Application No.PCT/US00/19539, Publication No. WO 01/06402, published on Jan. 25, 2001;International Application No. PCT/US00/19536, Publication No. WO01/06544, published on Jan. 25, 2001; International Application No.PCT/US00/19535, Publication No. WO 01/06268, published on Jan. 25, 2001;International Application No. PCT/US00/19540, filed on Jul. 20, 2001;pending Application Ser. No. 60/330,518, entitled “Method and apparatusfor wall film monitoring”, filed on Oct. 24, 2001; pending applicationSer. No. 60/330,555, entitled “Method and apparatus for electron densitymeasurement”, filed on Oct. 24, 2001; pending application 60/352,502,entitled “Method and apparatus for electron density measurement andverifying process status,” filed on Jan. 31, 2002; pending application60/352,546, entitled “Method and apparatus for determination and controlof plasma state,” filed on Jan. 31, 2002; pending application60/352,504, entitled “Method and apparatus for monitoring and verifyingequipment status,” filed on Jan. 31, 2002; pending application60/352,503, entitled “Apparatus and method for improving microwavecoupling to a resonant cavity,” filed on Jan. 31, 2002; and nowabandoned application 60/397,661, entitled “Method and system forelectron density measurement,” filed Jul. 23, 2002, which the presentapplication claims priority to. The contents of these applications areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to plasma processing and more particularlyto a diagnostic system for plasma processing comprising a man-machineinterface (MMI) and a remote MMI.

BACKGROUND OF THE INVENTION

The fabrication of integrated circuits (IC) in the semiconductorindustry typically employs plasma to create and assist surface chemistrywithin a plasma processing chamber necessary to remove material from anddeposit material to a substrate. In general, plasma is formed within theprocessing chamber under vacuum conditions by heating electrons toenergies sufficient to sustain ionizing collisions with a suppliedprocess gas. Moreover, the heated electrons can have energy sufficientto sustain dissociative collisions and, therefore, a specific set ofgases under predetermined conditions (e.g., chamber pressure, gas flowrate, etc.) are chosen to produce a population of charged species andchemically reactive species suitable to the particular process beingperformed within the chamber (e.g., etching processes where materialsare removed from the substrate or deposition processes where materialsare added to the substrate).

The semiconductor industry is constantly striving to produce smaller ICsand to increase the yield of viable ICs. Accordingly, the materialprocessing equipment used to process the ICs have been required to meetincreasingly more stringent performance requirements for etching anddeposition processes (e.g., rate, selectivity, critical dimension,etc.).

In order to meet the aforementioned challenges, plasma processingsystems are equipped with a variety of diagnostic systems in order toprovide comprehensive data necessary to tightly control a process.However, the diagnostic system employed in semiconductor manufacturingcan be complex and, in general, can require experienced personnel tooperate. Therefore, it is necessary to provide a user interface thatsimplifies and/or automates the use of such diagnostics systems.

SUMMARY OF THE INVENTION

The present invention relates to a method and system for monitoringelectron density during plasma processing. The present inventionadvantageously provides a method and system that enables semiconductormanufacturers to satisfy more stringent performance requirements formaterial processing equipment used in the semiconductor industry.

The present invention provides a diagnostic system for plasmaprocessing, the diagnostic system comprising: a multi-modal resonator; apower source coupled to the multi-modal resonator; a detector coupled tothe multi-modal resonator; and a controller coupled to the power sourceand the detector, wherein the controller provides at least one function,the at least one function including a Gunn diode voltage monitor, a Gunndiode current monitor, a varactor voltage monitor, a detector voltagemonitor, a varactor voltage control, a varactor voltage sweep control, aresonance lock-on control, a graphical user control, and an electrondensity monitor.

It is an object of the present invention that the controller furtherprovides a man-machine interface for performing the at least onefunction.

It is an object of the present invention that the controller furtherprovides a graphical user interface for performing the at least onefunction.

The present invention further provides a method of controlling thediagnostic system, the method comprising the steps of: activating thecontroller; selecting a varactor voltage control in order to control avaractor voltage of the power source; selecting a detector voltagemonitor in order to monitor a voltage from the detector; and adjustingthe varactor voltage for the power source using said controller.

The present invention further provides another method of controlling thediagnostic system, the method comprising the steps of: activating thecontroller; selecting a varactor voltage sweep control in order toautomatically control a varactor voltage of the power source; couplingthe varactor voltage to a display; and coupling the transmission signalfrom the detector to the display.

The present invention further provides another method of controlling thediagnostic system, the method comprising the steps of: activating thecontroller; selecting a resonance lock-on control; setting a varactorvoltage set point for a varactor voltage of the power source; andlocking the output frequency of the power source to the cavity resonanceof the multi-modal resonator by activating the varactor voltageset-point using the controller.

In an embodiment of the present invention, the diagnostic system furtherprovides a remote controller coupled to the controller, the remotecontroller provides a remote man-machine interface for performing the atleast one function.

The present invention further provides a method of remotely controllingthe diagnostic system using the remote man-machine interface, the methodcomprising the steps of: activating the controller; activating theremote man-machine interface; selecting a varactor voltage sweepcontrol; and activating the varactor voltage sweep control using defaultsettings.

It is a further object of the present invention to modify the defaultsettings prior to activating the varactor voltage sweep control.

The present invention further provides another method of remotelycontrolling the diagnostic system using the remote man-machineinterface, the method comprising the steps of: activating thecontroller; activating the remote man-machine interface; selecting aresonance lock-on control; and activating the resonance lock-on controlusing default settings.

It is a further object of the present invention to modify the defaultsettings prior to activating the resonance lock-on function.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages of the invention will become more apparentand more readily appreciated from the following detailed description ofthe exemplary embodiments of the invention taken in conjunction with theaccompanying drawings, where:

FIG. 1 shows a simplified block diagram of a diagnostic system accordingto an embodiment of the present invention;

FIG. 2 shows an enlarged, exploded, cross-sectional view of a microwavemirror having an aperture, a microwave window and associated mountingstructure according to an embodiment of the present invention;

FIG. 3 is a graphical representation of an exemplary cavity transmissionspectrum showing several longitudinal resonances and a respective freespectral range;

FIG. 4 shows a man-machine interface (MMI) for a diagnostic controlleraccording to an embodiment of the present invention;

FIG. 5 shows a man-machine interface (MMI) for a diagnostic controlleraccording to another embodiment of the present invention;

FIG. 6 presents an exemplary flow diagram of a controller according toan embodiment of the present invention;

FIG. 7 shows graphical user interface (GUI) screen for a remote MMI of aremote controller according to an embodiment of the present invention;

FIG. 8 shows graphical user interface (GUI) screen for a remote MMI of aremote controller according to another embodiment of the presentinvention;

FIG. 9 presents a method of controlling a diagnostic system according toan embodiment of the present invention;

FIG. 10 presents a method of controlling a diagnostic system accordingto another embodiment of the present invention;

FIG. 11 presents a method of controlling a diagnostic system accordingto another embodiment of the present invention;

FIG. 12 presents a method of controlling a diagnostic system accordingto another embodiment of the present invention;

FIG. 13 presents a method of controlling a diagnostic system accordingto another embodiment of the present invention; and

FIG. 14 presents a method of controlling a diagnostic system accordingto another embodiment of the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

The present invention generally relates to fabrication of integratedcircuits in the semiconductor industry. The present inventionadvantageously provides a method and apparatus that enablessemiconductor manufacturers to satisfy more stringent performancerequirements for material processing equipment used in the semiconductorindustry.

A method of improving the performance of material processing equipmentis to monitor and control plasma electron density within the processingchamber during the manufacturing process. Ideally, the plasma electrondensity is maintained such that the processes being performed areuniformly acting upon the entire surface of the substrate upon which aprocess is being performed.

An exemplary device used to measure plasma electron density is amicrowave system of suitably high frequency to exceed the electronplasma frequency. The device includes a pair of mirrors immersed in theplasma. Microwave power is coupled to a first microwave port on thefirst mirror and a detector is utilized to monitor the transmission ofmicrowave power through the resonant cavity formed by the opposingmirrors. The detector is either coupled to a second port on the firstmirror or a second port on the second mirror. For a Gaussian beam,cavity transmission occurs at discrete frequencies. The discretefrequencies correspond to an integer number of half wavelengths betweenthe apex of each mirror, as expressed by the following equation:

$\begin{matrix}{{v_{m,n,q} = {v_{0,0,q} = {\frac{c}{2\;{nd}}\left( {q + \frac{1}{2}} \right)}}},} & (1)\end{matrix}$

where ν_(0,0,q) is a resonant frequency of mode order q (assuming onlylongitudinal modes, i.e. m=n=0), c is the speed of light in a vacuum, nis the index of refraction for the medium bounded by the mirrors and dis the mirror spacing (apex-to-apex). For a vacuum, n=1, however, thepresence of plasma or, more specifically, a population of free electronsleads to a reduction of the index of refraction or an observableincrease (shift) of the cavity resonance frequencies ν_(0,0,q). For agiven mode q, the shift in frequency can be related to the index ofrefraction n and, thereafter, the (integrated) electron density <n_(e)>,is expressed by the following equation:

$\begin{matrix}{{\left\langle n_{e} \right\rangle \cong {\frac{8\;\pi^{2}ɛ_{o}}{e^{2}}v_{o}\Delta\; v}},} & (2)\end{matrix}$

for ν_(o)>>ω_(pe)/2π. For further details, the use of the above systemto measure plasma electron density is described in International App.No. PCT/US00/19539 (based upon U.S. Ser. No. 60/144,880), InternationalApp. No. PCT/US00/19536 (based upon U.S. Ser. No. 60/144,883),International App. No. PCT/US00/19535 (based upon U.S. Ser. No.60/144,878), and International App. No. PCT/US00/19540 (based upon U.S.Ser. No. 60/166,418), each of which is incorporated herein by referencein their entirety.

An embodiment of the plasma processing system 1 according to the presentinvention is depicted in FIG. 1. The plasma processing system 1 includesa plasma chamber 20 and a diagnostic system 30 for use in plasma chamber20. Diagnostic system 30 generally includes at least one multi-modalresonator 35, power source 60, detector 70, and controller 80.Controller 80 can, for example, include a computer or digital signalprocessor. Additionally, diagnostic system 30 can comprise a man-machineinterface (MMI) 82 coupled to the controller 80, a remote controller 84coupled to controller 80, and a remote MMI 86 coupled to the remotecontroller 84. Remote controller 84 can, for example, be a computer ordigital signal processor. Desirably, multi-modal resonator 35 comprisesan open resonant cavity having at least one reflecting surface, andreflecting surfaces can have planar and/or non-planar geometries. In apreferred embodiment, the reflecting surfaces are provided within plasmachamber 20. Alternatively, at least one reflecting surface can beprovided outside plasma chamber 20.

The plasma chamber 20 generally includes a base wall 22, an upper wall24, and side walls including a first side wall 26 and a second side wall27. The plasma chamber 20 also includes a substrate holder (or chuckassembly) 28 having a wafer plane 29, such as an upper surface of thesubstrate holder 28 upon which a substrate 14 is positioned in order tobe processed within the plasma chamber 20.

In a preferred embodiment, multi-modal resonator 35 comprises firstmicrowave mirror 40 coupled to power source 60 through a microwavewindow assembly 90, and second microwave mirror 50 coupled to detector70 through another microwave window assembly 90. Multi-modal resonatorextends along an axis generally parallel to a wafer plane of substrateholder 28 within plasma chamber 20.

In a preferred embodiment, the first microwave mirror 40 has a concavesurface 42 and is provided within the plasma chamber 20. The secondmicrowave mirror 50 has a concave surface 52 and is also provided withinthe plasma chamber 20. Alternately, the mirror surfaces can have flatand/or convex surfaces.

In the embodiment depicted in FIG. 1, the first mirror 40 is integratedwithin side wall 26 of the plasma chamber 20 and the second mirror 50 isintegrated within side wall 27 of the plasma chamber 20. The concavesurface 52 of the second microwave mirror 50 is oriented opposite theconcave surface 42 of the first microwave mirror 40. This geometry canbe referred to as a confocal geometry when the spacing between themirrors equals the radius of curvature of the mirrors. In an alternateembodiment, the mirrors are arranged in a semi-confocal configurationwherein a first mirror (comprising a concave surface of radius ofcurvature R) is located a distance d=R from a second mirror comprising aflat surface. In an alternate embodiment, the spacing d is adjusted tobe different than the radius of curvature of both mirrors in theconfocal arrangement or the radius of curvature of the first mirror inthe semi-confocal arrangement. In an alternate embodiment, the radius ofcurvature for each mirror is arbitrary. The selection of the spacing andrespective mirror radii of curvature is well known to those skilled inthe art of designing resonant cavities.

The power source 60 is coupled to a microwave window assembly 90 thatcomprises a first microwave mirror 40 and is configured to produce amicrowave signal. Desirably, the microwave signals within multi-modalresonator 35 extend along an axis 45 generally parallel to a wafer plane29 of a substrate holder 28. However, it is possible that the microwavesignals within multi-modal resonator 35 do not extend in a directiongenerally parallel to a wafer plane 29 of substrate holder 28.Controller 80 is coupled to power source 60 and is adapted to change atleast one of: an output frequency, an output power, an output phase, andan operating state of power source 60. For example, controller 80 cancause power source 60 to change its operational state at various timesbefore, during, and after a plasma has been established in plasmachamber 20.

Controller 80 is also coupled to detector 70. Desirably, detector 70 isconfigured to measure at least one transmitted microwave signal andprovide transmitted signal measurement data, and detector 70 isconfigured to measure at least one reflected microwave signal andprovide reflected signal measurement data. Alternately, detector 70 isconfigured to measure at least one transmitted microwave signal andprovide transmitted signal measurement data, or detector 70 isconfigured to measure at least one reflected microwave signal andprovide reflected signal measurement data.

In the embodiment depicted in FIG. 1, the microwave mirrors 40 and 50can be immersed within the process region 12 such that the concavesurfaces 42 and 52, respectively, oppose one another. Microwave power isinput from the power source 60 to the first mirror 40 via a microwavewindow assembly, and the detector 70 is configured to monitor cavitytransmission by being coupled to the opposite second mirror 50 using asecond microwave window assembly 90. The detector 70 can be coupled toeither the mirror opposite to the mirror to which microwave power isinput, as is the case in FIG. 1, or the detector can be coupled to thesame mirror to which microwave power is input (i.e. the first mirror 40in FIG. 1), or detectors can be coupled to both mirrors. As will bediscussed in further detail below, microwave windows are insertedbetween the microwave input and the detector, and the respectivemirror(s) to which the microwave input and the detector are connected,in order to preserve the integrity of the vacuum within the plasmaprocessing chamber 20.

FIG. 2 depicts a detailed schematic of a microwave window assembly 90for the first mirror 40. For example, a microwave window assembly can beused to provide a coupling from the power source 60 through an aperture44 in chamber wall 26 to the first mirror 40. A window assembly 90having substantially the same structure can be provided for the secondmirror 50, which is used to provide a coupling to the detector 70through an aperture 54 in chamber wall 27 from the second mirror 50.

The microwave window assembly 90 depicted in FIG. 2 includes a microwavewindow 92 that is mounted between a window flange 94 and a recessedsurface 47 of the first mirror 40. In the embodiment depicted in FIG. 2,the window 92 is provided within a recessed portion 48 on the rearsurface 46 of the first mirror 40. The microwave window 92 is providedbetween a first O-ring 96 provided on the window flange 94 and a secondO-ring 97 provided on the recessed surface 47 of the first mirror 40. Aplurality of fasteners 98 are provided to mechanically connect thewindow flange 94 to the first mirror 40 such that the microwave window92 is securely mounted within the recessed portion 48 on the rearsurface 46 of the first mirror 40. The window 92 is centered on awaveguide aperture 95 extending through the window flange 94 and thewaveguide aperture 44 extending through the first mirror 40. Therectangular waveguide apertures 44 and 95 are sized for a specificmicrowave band of operation and are fabricated using EDM. In analternate embodiment, the rectangular waveguide aperture 44 comprises arectangular cross-section with varying vertical and/or lateraldimensions. For example, waveguide aperture 44 can comprise a microwavehorn such as a pyramidal horn, an E-plane horn, or an H-plane horn.Details regarding the design and implementation of a microwave horn isdescribed in pending U.S. patent Ser. No. 60/352,503 (filed on Jan. 31,2002), incorporated herein by reference. In an alternate embodiment,waveguide apertures 44 and 95 are non-rectangular (e.g. circular). Ingeneral, processing material will form on the vacuum or process side ofthe window 92, however, the processing material will form at a ratedifferent than it will form on the mirror surface exposed to the plasma.The microwave window 92 is fabricated from a dielectric material such asalumina (sapphire), aluminum nitride, quartz, polytetrafluoroethylene(PTFE/Teflon), or Kapton. The window 92 is preferably fabricated fromsapphire due to its compatibility with the oxide etch processes.

The mirrors 40 and 50 are preferably fabricated from aluminum. Inalternative embodiments, the mirrors 40 and 50 are anodized withpreferably a 10 to 50 micron thick anodization or coated with a materialsuch as Yttria (Y₂O₃), aluminum oxide (Al₂O₃), or a combination of thetwo materials.

The microwave power source 60 is preferably an electronically tunablesource. For example, microwave power source 60 can be a voltagecontrolled Gunn diode oscillator (VCO). When the varactor diode of theVCO is biased with a direct current voltage, the output frequency of theVCO can be varied over some spectral range. Therefore, the VCOspecifications generally include center frequency, bandwidth and minimumoutput power. For example, at 35 GHz, a commercially available VCO is aWBV-28-20160RI Gunn diode oscillator offered by Millitech, LLC (20Industrial Drive East, South Deerfield, Mass. 01373-0109). Thespecifications for this VCO include a center frequency of 35 GHz withplus or minus 1 GHz bandwidth and a minimum output power of 40 mW. Thebias tuning range can generally extend from +25 V to −25 V, therebyadjusting this bias voltage leads to a change in the output frequency ofthe VCO. In alternative embodiments, operation at higher frequencies,such as 70 GHz and 105 GHZ, can be achieved using a frequency doubler(MUD-15-16F00) or tripler (MUT-10-16F00) with the above mentioned VCO.Using the above configuration, a center frequency of 70 GHz with plus orminus 2 GHz bandwidth and a minimum output power of 0.4 to 0.9 mW and acenter frequency of 105 GHz with plus or minus 3 GHz bandwidth and aminimum output power of 0.4 to 0.7 mW can be achieved, respectively. Ina preferred embodiment, a 94 GHz VCO (Model GV-10) is used and iscommercially available from Farran Technology LTD (Ballincollig, Cork,Ireland). The Model GV-10 VCO has a center frequency of 94 GHz with plusor minus 750 MHz bandwidth, a minimum output power of 10 mW, and avaractor tuning range of −0 to −25 V.

The detector 70 is preferably a general purpose diode detector such asthose commercially available from Millitech, LLC. For example, aDXP-15-RNFW0 and a DXP-10-RNFW0 are general purpose detectors in theV-band (50 to 75 GHz) and W-band (75 to 110 GHz), respectively.

Referring again to FIG. 1, controller 80 is coupled to power source 60and detector 70, and provides one or more functions for operating powersource 60, detector 70, and multi-modal resonator 35. Controller 80 canprovide monitoring functions such as a Gunn diode voltage monitor, aGunn diode current monitor, a varactor voltage monitor, a detectorvoltage monitor, and an electron density monitor. Furthermore,controller 80 can provide controlling functions including at least oneof a varactor voltage control, a varactor voltage sweep control, aresonance lock-on control, and a graphical user control.

As discussed earlier with reference to equation (1), transmissionthrough multi-modal resonator 35 occurs at discrete frequencies and,more specifically, at discrete frequencies where longitudinal resonanceexists. For example, when using a power source 60 comprising a voltagecontrolled oscillator (VCO), the frequency of microwave energy coupledto multi-modal resonator 35 can be varied, across the bandwidth of theVCO, by adjusting the bias voltage on the varactor diode. Therefore,adjusting the varactor bias voltage and, hence, the VCO frequency, andmonitoring the signal output from detector 70, the transmission spectrumcan be observed as shown in FIG. 3. FIG. 3 illustrates a typicaltransmission spectrum observed using a negative polarity detector,indicating the longitudinal resonances in frequency space and thespacing of the resonances or the free spectral range (FSR). In anembodiment, controller 80 provides a varactor voltage control permittingan operator to manually adjust the varactor voltage and, for example,monitor the detector output using an internal or external oscilloscopeor a computer, each of which is capable of presenting data via adisplay. In another alternate embodiment, controller 80 provides avaractor voltage sweep control permitting an automatic sweep of thevaractor voltage using an internally located waveform generator.Similarly, for example, the detector output can be monitored using aninternal or external oscilloscope or a computer, each of which iscapable of presenting data via a display. Both functions are discussedin greater detail below.

In another embodiment of the present invention, controller 80 provides aresonance lock-on control that includes a lock-on circuit coupled to thepower source 60 and the detector 70. The lock-on circuit can be utilizedto lock the output frequency of the power source 60 to a cavityresonance. The lock-on circuit superposes a dither signal (e.g. 1 kHz,10 mV amplitude square wave) on a direct current voltage substantiallynear the voltage and related output VCO frequency that corresponds witha pre-selected longitudinal frequency in multi-modal resonator 35 (i.e.the output frequency of the VCO falls within the “envelope” of theselected cavity longitudinal resonance). The transmission signaldetected by detector 70 is provided to the lock-on circuit, where it canrepresent a first derivative of the cavity transmission function(transmitted power versus frequency). The signal input to the lock-oncircuit from detector 70 provides an error signal by which the directcurrent component of the VCO bias voltage is adjusted to drive the VCOoutput frequency to the frequency associated with the peak of apre-selected longitudinal resonance as shown in FIG. 3. FIG. 3 presentsan exemplary cavity transmission spectrum (from a negative polaritydetector) indicating several longitudinal resonances and the respectivefree spectral range (FSR).

As described above, the introduction of plasma within the multi-modalresonator 35 causes a shift in frequency for each of the resonancesshown in FIG. 3 (i.e. each of the resonances shift to the right in FIG.3 when the electron density is increased or the index of refraction isdecreased according to equation (1)). Therefore, once the outputfrequency of the VCO is locked to a selected cavity resonance, thedirect current bias voltage with and without plasma can be recorded andthe frequency shift of the selected resonance is determined from thevoltage difference and the respective VCO calibration. For example, insubstrate processing, the direct current bias voltage is recorded once anew substrate is received by the process tool for materials processingand prior to the ignition of plasma. Hereinafter, this measurement willbe referred to as the vacuum resonance voltage. Once the plasma isformed, the direct current bias voltage is obtained as a function oftime for the given substrate and the time varying voltage difference orultimately electron density (via equation (2)) is recorded.

In another embodiment of the present invention, controller 80 provides agraphical user control that can be either locally located relative toplasma processing system 1 or remotely located relative to plasmaprocessing system 1. For example, the graphical user control can permitan operator to either locally or remotely perform the above describedcontrolling functions using a graphical user interface (GUI).

Each of the above identified monitoring and controlling functions arenow discussed in greater detail. FIG. 4 illustrates an exemplaryembodiment of a man-machine interface (MMI) 82 for controller 80.Alternately, MMI 82 can comprise a graphical user interface (GUI) screendisplayed on a computer screen. MMI 82 can comprise a monitor functionselection device 210 that permits the selection of Gunn diode voltagemonitor, Gunn diode current monitor, varactor voltage monitor, anddetector voltage monitor, wherein the respective signal can be displayedin display meter 220. Alternately, monitor function selection device 210and/ or display meter 220 can comprise a GUI. Additionally, MMI 82 cancomprise a control function selection device 230 that permits theselection of at least one of a varactor voltage control, a varactorvoltage sweep control, a resonance lock-on control, and a graphical usercontrol. Alternately, control function selection device 230 can comprisea GUI.

Controller 80 and MMI 82 can be made active by toggling an ON/OFF switch240. The ON/OFF switch 240 can power up the controller 80 and power upthe power source 60 following procedures determined by the manufacturerof power source 60. For example, a 94 GHz VCO (Model GV-10), availablefrom Farran Technology, requires that a voltage be applied to thevaractor diode first, followed by the appropriate voltage applied to theGunn diode. In another example, a 105 GHz VCO system, utilizing a 35 GHzVCO (WBV-28-20160RI) and a frequency tripler (MUT-10-16F00) availablefrom Millitech, LLC, does not require any order to biasing the varactordiode and the Gunn diode. Controller 80 comprises software programs forboth types of VCOs.

In addition, MMI 82 can comprise a plurality of status indicators. Forexample, MMI 82 can provide a first light emitting diode (LED) 242 toverify power to the controller 80, a second LED 244 to verifyapplication of a bias voltage to the varactor diode, and a third LED 246to verify application of a bias voltage to the Gunn diode. In general,power source 60 further requires setting limits on the minimum andmaximum voltage to be applied to the varactor diode and the Gunn diodein order to preserve the diodes and prevent them from failure. Thesevoltage limits can be set within controller 80. Alternately, a statusindicator can comprise a GUI.

MMI 80 can further comprise a second display meter 250 that displays thevaractor voltage. When control function selection device 220 is set tothe varactor voltage control function, a varactor voltage set pointdevice 260 can be used to manually adjust the voltage applied to thevaractor diode, wherein the respective voltage can be displayed ondisplay meter 250. Moreover, when the monitor function selection device210 is set to the detector voltage monitor, the detector voltage (orcavity transmission) can be monitored while manually sweeping thevaractor diode voltage. Alternately, second display meter 250 cancomprise a GUI. When the control function selection device 210 is set tothe resonance lock-on control, the voltage applied to the varactor diodecan be adjusted using the varactor voltage set point device 260 and theamplitude of the dither voltage employed by the lock-on circuit can beset using a dither amplitude set point device 270. Varactor voltage setpoint device 260 and dither amplitude set point device 270 can be, forexample, potentiometers. Alternately, varactor voltage set point device260 and dither amplitude set point device 270 can comprise a GUI. Whenattempting to lock-on to a cavity resonance, the varactor voltage setpoint is adjusted to a voltage adjacent a varactor voltage correspondingto a cavity resonance (e.g. select a voltage residing somewhere betweencavity resonances as shown in FIG. 3). Once the varactor voltage and thedither amplitude are set, the varactor voltage set point can beactivated by, for example, toggling the lock-on set point switch 280.Activation of the varactor voltage set point sets the varactor voltageto the set point value, thus allowing the lock-on circuit to lock theoutput frequency of power source 60 to the selected cavity resonance. Asthe varactor voltage approaches the resonance envelope of a cavityresonance, the lock-on circuit can determine an error signal enabling itto lock-on to the respective cavity resonance. A successful lock to acavity resonance can be determined by setting the monitor functionselection device 210 to varactor diode voltage and monitoring thisvoltage in display meter 220. Once the varactor bias voltage reaches asteady value (not at the minimum or maximum voltage limits), the outputfrequency of power source 60 can be determined to be locked to a cavityresonance.

FIG. 5 illustrates an exemplary panel of controller 80. A powerreceptacle 282 is provided for coupling controller 80 to a (AC) poweroutlet using a power cable. A varactor voltage output test point 284 canbe provided in order to couple the varactor voltage signal to anothermeasurement device such as an oscilloscope or voltmeter. The varactorvoltage output test point 284 can be, for example, a SMA or BNCconnection. A graphical user control connection 286 can be provided tocouple controller 80 to remote controller 84. The remote controlconnection 286 can be, for example, a 15-pin connector. A power sourceconnection 288 is provided in order to couple controller 80 to powersource 60. A pair of detector connections, 290 and 292, and a polaritytoggle switch 294 can be provided to couple controller 80 to detector70. Depending on the polarity of detector 70 (i.e. positive ornegative), the appropriate detector connection 290, 292 can be selectedand the polarity toggle switch can be properly set.

FIG. 6 presents an exemplary flow diagram 300 for controller 80 todescribe the flow logic for enabling the monitoring and controllingfunctions described in FIGS. 4 and 5. As described above, controlfunction selection device 230 can permit the selection of one of thefollowing control functions: varactor voltage control, a varactorvoltage sweep control, a resonance lock-on control, and a graphical usercontrol.

When the varactor voltage sweep control is selected, the signal coupledto isolated output 350 originates from the varactor voltage set pointdevice 260. The isolated output 350 permits referencing the varactorvoltage to a voltage other than ground potential (if necessary). Forexample, a 94 GHz VCO (Model GV-10), available from Farran Technology,requires that the varactor voltage be referenced to the positive node ofthe Gunn diode voltage. In another example, a 105 GHz VCO system,utilizing a 35 GHz VCO (WBV-28-20160RI) and a frequency tripler(MUT-10-16F00) available from Millitech, LLC, requires that the varactorvoltage be referenced to ground potential. When the varactor voltagesweep function is selected, the signal coupled to isolated output 350originates from a sweep generator 340. Sweep generator 340 can, forexample, comprise a saw-tooth waveform generator.

When the resonance lock-on control function is selected, the signalinput to isolated output 350 originates from the lock-on circuit 310.Lock-on circuit 310 can comprise a clock and dither circuit 320 tosample a first signal 322 from detector 70 during the positive halfcycle of the square wave dither and a second signal 324 from detector 70during the negative half cycle of the square wave dither. The firstsignal 322 and the second signal 324 are input to an error generatorcircuit 330, wherein an error signal 332 is generated and coupled to theisolated output 350.

As described earlier, the ON/OFF switch 240 can power up the controller80 and power up the power source 60 following procedures determined bythe manufacturer of power source 60. For example, a 94 GHz VCO (ModelGV-10), available from Farran Technology, requires that a voltage beapplied to the varactor diode first, followed by the appropriate voltageapplied to the Gunn diode. In another example, a 105 GHz VCO system,utilizing a 35 GHz VCO (WBV-28-20160RI) and a frequency tripler(MUT-10-16F00) available from Millitech, LLC, does not require any orderto biasing the varactor diode and the Gunn diode. In FIG. 6, a timingcircuit 360 is coupled to the isolated output 350 in order to assurethat, during power ON, the varactor diode is biased before the Gunndiode, and, during power OFF, the bias to the Gunn diode is removedbefore the bias to the varactor diode.

The output of the timing circuit 360 is coupled to the power source 60and to a current monitor 370, wherein the Gunn current can bedetermined.

Additionally, FIG. 6 identifies an input circuit 380 coupled to detector70, wherein the input circuit 380 can provide gain to the signalreceived from detector 70.

When the graphical user control is selected, the signal input toisolated output 350 originates from signal commands input through remotecontrol connection 286. For example, remote controller 84 can be coupledto the remote control connection 286 in order to execute the monitoringand controlling functions provided by controll 80. Using this example,the graphical user control is now discussed in greater detail below.

Referring again to FIG. 1, remote controller 84 is coupled to controller80, wherein remote controller 84 provides a remote MMI 86 for anoperator to remotely control the diagnostic system 30 when the controlfunction selection device 230 is set to the graphical user control.

In a preferred embodiment, the remote MMI 86 includes software that isinstalled onto remote controller 84. Desirably, the installation of thesoftware on remote controller 84 causes an icon to be displayed on theremote controller's display. For example, double-clicking the icon cancause the software to begin executing to provide the remote MMI 86.Desirably, a login screen is displayed, and the login screen is used tocontrol access to the remote MMI 86.

In a preferred embodiment, the computer 84 includes MMI software forcontrolling the remote MMI 86. Remote MMI 86 includes a GUI screen 400for performing the varactor voltage sweep function and for performingthe resonance lock-on function. GUI screen 400 is an easily readablestatus display and control interface for use with the controller 80.Visible warning signals are present on the GUI screen, and interlockscan be provided by the MMI software. In addition, remote MMI 86 includesinput devices, such as a touchscreen, a mouse, and/or a keyboard.

FIG. 7 presents GUI screen 400 that enables an operator to perform thevaractor voltage sweep function in order to observe the cavityresonances in multi-modal resonator 35. When using the graphical usercontrol, the sweep function can be generated internally within remotecontroller 84, as indicated in FIG. 6, or internally within thecontroller 80. GUI screen 400 can provide a setup panel 410, a datadirectory panel 420, a graph panel 430, a lock-on sample panel 440, aplot panel 450, a mode panel 460, and a display panel 470.

Setup panel 410 provides a plurality of setup parameters. The pluralityof setup parameters can include setting a minimum varactor diode sweepvoltage 412, and a maximum varactor diode sweep voltage 414. Setup panel410 can further provide setup parameters including setting a ditheramplitude 416, and a varactor voltage set point 418.

Data directory panel 420 permits setting a directory location 422 forstoring data acquired using the remote MMI 86.

Graph panel 430 permits setting a data scale factor 432 and a data filename 434, and performing a print action 436, a copy action 437, and ascale action 438. The data scale factor 432 can be employed to set thenumber of data points recorded during data acquisition. For example, themaximum number of data points can be 8192 when the scale factor is givenan integer value of unity (1), and the number of data points acquiredcan be reduced by increasing the integer value of the scale factor 432,e.g. the number of points N=8192/{2^((j−1))}, where j represents theinteger value of the scale factor 432. A default naming convention forthe data file name 434 can comprise a date stamp given by“MMDDYYYYhhmmsst”, where MM=Month from 01 to 12, DD=Day from 01 to 31,YYYY=Year, hh=hours from 00 to 24, mm=minutes from 00 to 60, ss=secondsfrom 00 to 60, and t=tenths of seconds from 0 to 9 (e.g.“032920020930101” represents 10.1 seconds past 09:30 AM on Mar. 29,2002). Print action 436 can permit printing a plot displayed indisplayed panel 470 directly to a printer, or a print-ready file such aspostscript, encapsulated postscript, PDF, TIFF, JPG, BMP, etc. Copyaction 437 can permit copying the plot present in display panel 470, andstoring the plot in buffer memory. The stored plot can then be pastedwithin a document such as a WORD document, a POWERPOINT document, etc.Scale action 438 permits scaling the plot present in display panel 470based upon the determined ordinate and abscissa ranges from the acquireddata.

Plot panel 450 permits the operator to select one or more dataparameters including the varactor diode voltage, the Gunn diode voltage,the Gunn diode current, and the detector voltage for plotting in displaypanel 470.

Mode panel 460 permits the operator to select the control function mode462, and the data acquisition mode 464. When the varactor voltage sweepfunction is selected, the control function mode 462 can read “SWEEP”,and when the resonance lock-on function is selected, the controlfunction mode 462 can read “LOCK-ON”. FIG. 7 presents GUI screen 400when the control function mode 462 is set to “SWEEP”. The dataacquisition mode 464 can, for example, be set to “Log” in order torecord acquired data to a data file defined by the data file name 434 ina file directory defined by the directory location 422, or “No Log” inorder to disable recording data to a data file.

GUI screen 400 can further provide a varactor voltage display 480, aGunn diode voltage display 482, a Gunn diode current display 484, and adetector voltage display 486 in order to, for example, permit anoperator to diagnose the status of the diagnostic system 30. Displays480, 482, 484, 486 can be updated at a pre-set frequency, hence,providing real-time data to the operator for diagnosing the status ofthe power source 60.

Display panel 470 can permit a presentation of data selected in plotpanel 450. For example, the data presented in plot panel 450 can beselected by activating one or more of the plot variables includingvaractor voltage plot 452, Gunn diode voltage plot 454, Gunn diodecurrent plot 456, and detector voltage plot 458. In FIG. 7, displaypanel 470 presents an exemplary cavity transmission spectrum.

GUI screen 400 can further provide an action mode 490 that permits theoperator to execute the varactor diode voltage sweep and display data inthe display panel 470.

FIG. 8 presents the GUI screen 400 when the control function mode 462 isset to “LOCK-ON”. Setting the control function mode 462 to “LOCK-ON”permits the operator to perform the resonance lock-on control.

Setup panel 410 can further provide setup parameters including setting adither amplitude 416, and a varactor voltage set point 418. Both thedither amplitude 416 and the varactor voltage set point can be set in amanner similar to that described above.

Lock-on panel 440 can permit setting one or more data acquisitionparameters. The data acquisition parameters can include a sample rate442, a sample duration 444, and a sample mode 446. The sample rate 442can, for example, comprise the number of data points acquired persecond. The sample duration 444 can, for example, comprise the timeduration for the sample. The sample mode 446 can, for example, be set to“ON” in order to store acquired data to permanent memory, or be set to“OFF” in order to disable storing acquired data to permanent memory.

Display panel 470 can permit a presentation of data selected in plotpanel 450. In FIG. 8, display panel 470 presents an exemplary time traceof the varactor diode voltage during a plasma “ON” condition atapproximately 12 seconds and plasma “OFF” condition at approximately 24seconds. As described in equation (2), the electron density isproportional to the shift in frequency of a cavity resonance, or duringlock-on the difference between the varactor voltage with a plasma andthe varactor voltage without a plasma.

FIG. 9 presents a method controlling a diagnostic system according to anembodiment of the present invention. A flow diagram 600 begins in 610with activating the controller for the diagnostic system. The diagnosticsystem can be a plasma diagnostic system and, for example, it cancomprise the multi-modal resonator, the power source, the detector, andthe controller described above. Activation of the controller can occur,for example, by toggling the ON/OFF switch. Alternately, activation ofthe controller can, for example, further include activating a remotecontroller.

In 620, the control function is set to the varactor voltage control. In630, the monitor function is set to the detector voltage. In 640, thevaractor voltage can be adjusted using the varactor voltage set pointdevice. Alternately, the varactor voltage can be adjusted using a GUIcoupled to the controller. Alternately, the varactor voltage can beadjusted using a GUI provided by a remote MMI coupled to the remotecontroller.

FIG. 10 presents a method of controlling a diagnostic system accordingto another embodiment of the present invention. A flow diagram 700begins in 710 with activating the controller for the diagnostic system.The diagnostic system can be a plasma diagnostic system and, forexample, it can comprise the multi-modal resonator, the power source,the detector, and the controller described above. Activation of thecontroller can occur, for example, by toggling the ON/OFF switch.Alternately, activation of the controller can, for example, furtherinclude activating a remote controller.

In 720, the control function is set to the varactor voltage sweepcontrol. In an embodiment of the present invention, the varactor voltagesweep control enables the use of an internal sweep waveform generator inthe controller using preset limits for the minimum and maximum sweepvoltages set in the controller hardware. In an alternate embodiment, theminimum and maximum sweep voltages are set using a GUI. In an alternateembodiment, the minimum and maximum sweep voltages are set using a GUIprovided by a remote MMI coupled to a remote controller. Alternately,the minimum and maximum sweep voltages can be default values stored inmemory provided by the controller. In 730, the varactor voltage iscoupled to a display. For example, the display can be provided by aninternal or external oscilloscope, or a computer. The varactor voltagecan, for example, be coupled from the controller to the oscilloscopeusing a coaxial cable connected to the varactor voltage output testpoint and connected to the front panel (e.g. channel no. 1) of theoscilloscope. In 740, the detector voltage is coupled to a display.Similarly, for example, the display can be provided by an internal orexternal oscilloscope, or a computer. The detector voltage can, forexample, be coupled from the controller to the oscilloscope using acoaxial cable connected to the detector connection and connected to thefront panel (e.g. channel no. 2) of the oscilloscope.

FIG. 11 presents a method of controlling a diagnostic system accordingto another embodiment of the present invention. A flow diagram 800begins in 810 with activating the controller for the diagnostic system.The diagnostic system can be a plasma diagnostic system and, forexample, it can comprise the multi-modal resonator, the power source,the detector, and the controller described above. Activation of thecontroller can occur, for example, by toggling the ON/OFF switch.Alternately, activation of the controller can, for example, furtherinclude activating a remote controller.

In 820, the control function is set to the resonance lock-on control. Inan embodiment of the present invention, the resonance lock-on controlenables the use of lock-on circuit provided in the controller using apreset dither amplitude and varactor voltage set point. In an alternateembodiment, the dither amplitude and the varactor voltage set point areset using a GUI. In an alternate embodiment, the dither amplitude andthe varactor voltage set point are set using a GUI provided by a remoteMMI coupled to a remote controller. Alternately, the dither amplitudeand the varactor voltage set point can be default values stored inmemory provided by the controller. In 830, the varactor voltageset-point is set. Typically, the varactor voltage set-point is set to avalue adjacent a selected cavity resonance. In 840, the lock-onset-point switch is toggled to apply the varactor voltage set-pointvoltage to the varactor diode. Thereafter, the varactor voltage driftsuntil lock-on is achieved. Once lock-on is achieved, the diagnosticsystem can be used to monitor, for example, the electron density in themulti-modal resonator.

FIG. 12 presents a method of computing an electron density in amulti-modal resonator according to another embodiment of the presentinvention. A flow diagram 850 begins in 860 with locking the powersource to a cavity resonance using, for example, the method described inFIG. 11. In 870, the varactor voltage is recorded via a data acquisitionsystem such as an oscilloscope, an A/D converter, a computer, anoperator, etc. In 880, a varactor voltage difference is determined bycomputing the difference between the varactor voltage observed withoutplasma in the multi-modal resonator and the varactor voltage observedwith plasma in the multi-modal resonator. In 890, an electron density iscomputed from the varactor voltage difference using the varactorvoltage-frequency calibration of the power source and equation (2). Thevaractor voltage can be recorded and stored in temporary memory, whereinthe varactor voltage difference and electron density are computed, andthe electron density is displayed and/or stored to permanent memory. Inan alternate embodiment, the varactor voltage is recorded and stored inpermanent memory, wherein the varactor voltage difference and electrondensity are computed either during processing or during post-processing,and the electron density is displayed and/or stored to permanent memory.

FIG. 13 presents a method of controlling a diagnostic system accordingto another embodiment of the present invention. A flow diagram 900begins in 910 with activating the controller for the diagnostic system.The diagnostic system can be a plasma diagnostic system and, forexample, it can comprise the multi-modal resonator, the power source,the detector, and the controller described above. Activation of thecontroller can occur, for example, by toggling the ON/OFF switch.

In 920, the remote MMI is activated. Activation of the remote MMI can,for example, comprise turning on the remote controller hosting the MMIsoftware, and executing the MMI software to initiate the GUI screen forthe remote MMI. In 930, the control function mode is set to sweep modeby activating the control function mode. For example, the controlfunction mode can be set in the mode panel of the GUI screen to read“SWEEP” using, for example, keyboard entry, mouse entry, etc. Ingeneral, the varactor voltage sweep function of the remote MMI can beset as the default configuration.

In 940, the default settings for the varactor voltage sweep function canbe checked. If the settings are acceptable, then the varactor voltagesweep can be activated by toggling the remote MMI action mode. As thevaractor voltage sweep function is performed, the plot of the defaultplot variables is presented in the display panel of the GUI screen. Ifchanges are necessary, then the settings can be adjusted in 960 through995. In 960, the minimum and maximum varactor voltages for the sweep canbe varied in the setup panel of the GUI screen using, for example,keyboard entry, mouse entry, etc. In 970, the data directory for storingacquired data can be varied in the data directory panel of the GUIscreen using, for example, keyboard entry, mouse entry, etc. In 980, theplot scale factor (i.e. number of data points in varactor voltage sweep)can be varied in the graph panel of the GUI screen using, for example,keyboard entry, mouse entry, etc. In 990, the plot variables (i.e.varactor diode voltage, Gunn diode voltage, Gunn diode current, ordetector voltage) can be selected in the plot panel of the GUI screenusing, for example, keyboard entry, mouse entry, etc. In 995, the dataacquisition mode (i.e. enable recording data acquisition to permanentmemory or disable recording data acquisition to permanent memory) can beset in the mode panel of the GUI screen using, for example, keyboardentry, mouse entry, etc.

Following adjustments to the settings, the varactor voltage sweepfunction is performed and the plot of the selected plot variables ispresented in the display panel of the GUI screen in 950.

FIG. 14 presents a method of controlling a diagnostic system accordingto another embodiment of the present invention. A flow diagram 1000begins in 1010 with activating the controller for the diagnostic system.The diagnostic system can be a plasma diagnostic system and, forexample, it can comprise the multi-modal resonator, the power source,the detector, and the controller described above. Activation of thecontroller can occur, for example, by toggling the ON/OFF switch.

In 1020, the remote MMI is activated. Activation of the remote MMI can,for example, comprise turning on the remote controller hosting the MMIsoftware, and executing the MMI software to initiate the GUI screen forthe remote MMI. In 1030, the control function mode is set to lock-onmode by activating the control function mode. For example, the controlfunction mode can be set in the mode panel of the GUI screen to read“LOCK-ON” using, for example, keyboard entry, mouse entry, etc. Ingeneral, the resonance lock-on function of the remote MMI can be set asthe default configuration.

In 1040, the default settings for the resonance lock-on function can bechecked. If the settings are acceptable, then the resonance lock-onfunction can be activated by toggling the remote MMI action mode. As theresonance lock-on is performed, the plot of the default plot variablesis presented in the display panel of the GUI screen. If changes arenecessary, then the settings can be adjusted in 1060 through 1095. In1060, the dither amplitude and/or the varactor voltage set-point can bevaried in the setup panel of the GUI screen using, for example, keyboardentry, mouse entry, etc. In 1070, the data directory for storingacquired data can be varied in the data directory panel of the GUIscreen using, for example, keyboard entry, mouse entry, etc. In 1080,the plot scale factor (i.e. number of data points in varactor voltagesweep) can be varied in the graph panel of the GUI screen using, forexample, keyboard entry, mouse entry, etc. In 1090, the sample and plotvariables (i.e. sample rate and/or sample duration, and varactor diodevoltage, Gunn diode voltage, Gunn diode current, or detector voltage)can be selected in the graph and plot panels of the GUI screen using,for example, keyboard entry, mouse entry, etc. In 1095, the dataacquisition mode (i.e. enable recording data acquisition to permanentmemory or disable recording data acquisition to permanent memory) can beset in the sample and/or mode panels of the GUI screen using, forexample, keyboard entry, mouse entry, etc.

Following adjustments to the settings, the resonance lock-on function isperformed and the plot of the selected plot variables is presented inthe display panel of the GUI screen in 1050.

Although only certain exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

1. A diagnostic system for plasma processing, said diagnostic systemcomprising: a multi-modal resonator; a power source, including a Gunndiode voltage controlled oscillator (VCO), coupled to said multi-modalresonator; a detector coupled to said multi-modal resonator; acontroller coupled to said power source and said detector, wherein saidcontroller provides at least one monitoring function and at least onecontrolling function, said at least one monitoring function including atleast one of a Gunn diode voltage monitor, a Gunn diode current monitor,a varactor voltage monitor, an electron density monitor, and a detectorvoltage monitor, and said at least one controlling function including atleast one of a varactor voltage control, a varactor voltage sweepcontrol, a resonance lock-on control, and a graphical user control; anda programmable user interface connected to said controller, saidprogrammable user interface selecting said at least one monitoringfunction and said at least one controlling function in the diagnosticsystem.
 2. The diagnostic system as recited in claim 1, wherein saiduser interface includes a man-machine interface (MMI) for performingsaid at least one function.
 3. The diagnostic system as recited in claim2, wherein said MMI displays at least one of a Gunn diode voltage, aGunn diode current, a varactor voltage, and a detector voltage.
 4. Thediagnostic system as recited in claim 2, wherein said varactor voltagecontrol function provides the capability for varying the varactorvoltage on said Gunn diode VCO using said MMI.
 5. The diagnostic systemas recited in claim 2, wherein said varactor voltage sweep functionprovides the capability for automatically varying the varactor voltageon said Gunn diode VCO using said MMI.
 6. The diagnostic system asrecited in claim 5, wherein said automatically varying the varactorvoltage on said Gunn diode VCO comprises activating a sweep generatorpackaged in said controller using said MMI.
 7. The diagnostic system asrecited in claim 2, wherein said resonance lock-on function comprisesactivating a lock-on circuit packaged in said controller, setting avaractor voltage set-point, and activating said varactor voltageset-point.
 8. The diagnostic system as recited in claim 1, wherein saidcontroller is further coupled to a remote controller, and saidcontroller permits remote control of said controller using said remotecontroller.
 9. The diagnostic system as recited in claim 8, wherein saidremote controller provides a remote man-machine interface (MMI) forremotely performing said at least one function provided by saidcontroller.
 10. The diagnostic system as recited in claim 9, whereinsaid remote man-machine interface comprises a graphical user interface(GUI).
 11. The diagnostic system as recited in claim 9, wherein saidman-machine interface comprises executing software on said remotecontroller.
 12. The diagnostic system as recited in claim 10, whereinsaid graphical user interface provides a setup panel for presenting aplurality of setup parameters.
 13. The diagnostic system as recited inclaim 12, wherein said plurality of setup parameters comprises at leastone of a minimum varactor diode sweep voltage, a maximum varactor diodesweep voltage, a dither amplitude, and a varactor voltage set point. 14.The diagnostic system as recited in claim 10, wherein said graphicaluser interface provides a data directory panel, said data directorypanel permits setting a directory location for storing data acquiredusing said remote man-machine interface.
 15. The diagnostic system asrecited in claim 10, wherein said graphical user interface provides agraph panel, said graph panel permits at least one of setting a datascale factor, setting a data file name, performing a print action,performing a copy action, and performing a scale action.
 16. Thediagnostic system as recited in claim 10, wherein said graphical userinterface provides a display panel for presenting at least one dataparameter.
 17. The diagnostic system as recited in claim 16, whereinsaid data parameter includes a Gunn diode voltage, a Gunn diode current,a varactor diode voltage, and a detector voltage.
 18. The diagnosticsystem as recited in claim 16, wherein said graphical user interfacefurther provides a plot panel for selecting said at least one dataparameter.
 19. The diagnostic system as recited in claim 10, whereinsaid graphical user interface provides a mode panel for selecting atleast one of a control function mode and a data acquisition mode. 20.The diagnostic system as recited in claim 19, wherein said controlfunction modes comprises at least one of a varactor voltage sweepfunction and a resonance lock-on function.
 21. The diagnostic system asrecited in claim 19, wherein said data acquisition mode comprises atleast one of enabling data storage to a data file and disabling datastorage to a data file.
 22. The diagnostic system as recited in claim19, wherein said graphical user interface provides an action mode, saidaction mode permits an operator to execute said control function mode.23. The diagnostic system as recited in claim 19, wherein said graphicaluser interface provides a lock-on panel for setting at least one dataacquisition parameter.
 24. The diagnostic system as recited in claim 23,wherein said data acquisition parameters include a sample rate, a sampleduration, and a sample mode.
 25. The diagnostic system as recited inclaim 1, wherein said controller further provides a graphical userinterface (GUI) for performing said at least one function.
 26. A methodof controlling a diagnostic system, said diagnostic system comprising amulti-modal resonator to produce a cavity resonance, a power source toproduce an output frequency, a detector to produce a transmissionsignal, a controller coupled to said power source and said detector, anda user interface connected to said controller and programmable to selectat least one monitoring function and at least one controlling function,said method comprising: activating said controller; selecting from saiduser interface a varactor voltage control in order to control a varactorvoltage of said power source; selecting from said user interface adetector voltage monitor in order to monitor said transmission signalfrom said detector; and adjusting said varactor voltage for said powersource using said controller.
 27. The method as recited in claim 26,wherein said user interface comprises a man-machine interface forperforming at least one of setting said control function, setting saidmonitor function, and adjusting said varactor voltage.
 28. The method asrecited in claim 26, wherein said controller provides a graphical userinterface for performing at least one of setting said control function,setting said monitor function, and adjusting said varactor voltage. 29.A method of controlling a diagnostic system, said diagnostic systemcomprising a multi-modal resonator to produce a cavity resonance, apower source to produce an output frequency, a detector to produce atransmission signal, a controller coupled to said power source and saiddetector, and a user interface connected to said controller andprogrammable to select at least one monitoring function and at least onecontrolling function, said method comprising: activating saidcontroller; selecting from said user interface a varactor voltage sweepcontrol in order to automatically control a varactor voltage of saidpower source; coupling said varactor voltage to a display; and couplingsaid transmission signal from said detector to said display.
 30. Themethod as recited in claim 29, wherein said display comprises at leastone of a computer, a digital signal processor, and an oscilloscope. 31.The method as recited in claim 29, wherein said user interface comprisesa man-machine interface for performing said setting said controlfunction.
 32. The method as recited in claim 29, wherein said controllerprovides a graphical user interface for performing said setting saidcontrol function.
 33. A method of controlling a diagnostic system, saiddiagnostic system comprising a multi-modal resonator to produce a cavityresonance, a power source to produce an output frequency, a detector toproduce a transmission signal, a controller coupled to said power sourceand said detector and configured to provide a lock-on circuit forreceiving said transmission signal from said detector and locking saidoutput frequency of said power source to said cavity resonance of saidmulti-modal resonator, and a user interface connected to said controllerand programmable to select at least one monitoring function and at leastone controlling function, said method comprising: activating saidcontroller; selecting from said user interface a resonance lock-onfunction; selecting from said user interface a varactor voltage of saidpower source; and locking said output frequency of said power source tosaid cavity resonance of said multi-modal resonator by activating avaractor voltage set-point using said controller.
 34. The method asrecited in claim 33, wherein said method further comprises the step of:measuring an electron density in said multi-modal resonator, whereinsaid measuring said electron density comprises the steps of: recordingsaid varactor voltage corresponding to said locking said outputfrequency of said power source to said cavity resonance of saidmulti-modal resonator; determining a difference between said varactorvoltage with plasma in said multi-modal resonator and said varactorvoltage without plasma in said multi-modal resonator; and computing saidelectron density from said difference.
 35. The method as recited inclaim 33, wherein said user interface comprises a man-machine interfacefor setting said control function, setting said varactor voltageset-point, and activating said varactor voltage set-point.
 36. Themethod as recited in claim 33, wherein said controller provides agraphical user interface for setting said control function, setting saidvaractor voltage set-point, and activating said varactor voltageset-point.
 37. A method of controlling a diagnostic system, saiddiagnostic system comprising a multi-modal resonator to produce a cavityresonance, a power source to produce an output frequency, a detector toproduce a transmission signal, a controller coupled to said power sourceand said detector, a remote controller coupled to said controller, and auser interface connected to said remote controller and programmable toselect at least one monitoring function and at least one controllingfunction, said method comprising: activating said controller; activatingsaid user interface; selecting from said user interface a varactorvoltage sweep control; and activating said varactor voltage sweepcontrol using default settings.
 38. The method as recited in claim 37,wherein said method further comprises modifying said default settingsprior to activating said varactor voltage sweep function.
 39. The methodas recited in claim 38, wherein said modifying said default settingscomprises modifying at least one of a minimum varactor diode voltage, amaximum varactor diode voltage, a data directory for storing acquireddata, a scale, a plot variable, and a data acquisition mode.
 40. Amethod of controlling a diagnostic system, said diagnostic systemcomprising a multi-modal resonator to produce a cavity resonance, apower source to produce an output frequency, a detector to produce atransmission signal, a controller coupled to said power source and saiddetector and configured to provide a lock-on circuit for receiving saidtransmission signal from said detector and locking said output frequencyof said power source to said cavity resonance of said multi-modalresonator, a remote controller coupled to said controller, and a userinterface connected to said remote controller and programmable to selectat least one monitoring function and at least one controlling function,said method comprising: activating said controller; activating saidrface; selecting from said user interface a resonance lock-on control;and activating said resonance lock-on control using default settings.41. The method as recited in claim 40, wherein said method furthercomprises modifying said default settings prior to activating saidresonance lock-on control.
 42. The method as recited in claim 41,wherein said modifying said default settings comprises modifying atleast one of a dither amplitude, a varactor voltage set-point, a datadirectory for storing acquired data, a scale, a plot variable, a samplerate, a sample duration, and a data acquisition mode.